In the earlier P2P transmission, Application Layer Multi-cast (ALM) distribution tree technology is adopted, in which, medial nodes redistribute content and leaf nodes receive the content. This method is troubled with two problems. The loads undertaken by the medial nodes are very heavy, while the upload bandwidth of the leaf nodes is not utilized to distribute the contents.
One improved method is that the source nodes divide the content into a plurality of blocks, and then respectively transmit them to each node. Each node then retransmits them to other nodes. The improvement of this method is that each node (possibly all the nodes) are used for upload, but the difference of the upload bandwidth between each node is not yet used.
A further improved method is that it also divides the content into a plurality of blocks. The number of the blocks redistributed by a certain node is proportional to the upload bandwidth of the node. The node with larger upload bandwidth can redistribute many blocks, while the node with smaller upload bandwidth can redistribute less blocks. This method makes full use of the upload bandwidth of each node. But further improvement is also required, because this method is unfair. It may increase the unnecessary load for certain nodes. For example, if a content download requires bandwidth B, herein three nodes can undertake the task, and then totally 3B of upload bandwidth is required to provide transmission for them. Yet their base upload bandwidths are respectively B, 0B and 5B. Therefore, they respectively contributed 0.5B, 0B and 2.5B upload bandwidth. Obviously, there is no necessity for the node contributed 2.5B to provide another more 0.5B upload bandwidth for a node with the capability. Generally, it is recommended to help the node with difficulty, but not the nodes with the capability in a way of robbing the rich.
On the other hand, download of a group of users in P2P transmission requires the support of corresponding upload. In a certain period, download summation equals to the upload summation. Total upload bandwidth should be larger than the total bandwidth required for download. When the total bandwidth of upload is not satisfied, there will be no way to download. Therefore, the method for controlling transmission rate and traffic is required.